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Treatment of functional (hormone-making) pituitary tumors

The treatment of functional pituitary tumors depends on which type of hormone they make.

Treatment of prolactin-secreting adenomas (prolactinomas)

Unlike most other pituitary tumors, surgery is usually not the first treatment for these tumors. Instead, medicines that block the production of prolactin (cabergoline or bromocriptine) are used first (see “Medicines to treat pituitary tumors”). They work so well that surgery is usually not needed. Although both of these drugs are effective, cabergoline seems to work better and may have fewer side effects. It also lasts longer, so it does not need to be taken as often as bromocriptine.

Most patients can control their prolactin levels with these medicines. The drugs also shrink most prolactin-secreting macroadenomas. Only about 1 out of 5 of these tumors doesn’t shrink after treatment. Even when the tumors don’t shrink, these drugs usually keep them from growing larger.

Within 3 months of starting treatment, the blood prolactin level is measured again and an MRI scan of the pituitary is done to check if the medicine is working. If so, treatment may be continued for the rest of the patient’s life. In some people, if treatment with these medicines has been successful and MRI scans show a prolonged period with no tumor remaining, the treatment may be stopped. These people will need to have regular MRIs to see if the tumor comes back. On the other hand, if after 6 months the tumor hasn’t responded well enough to treatment, or if serious side effects occur, then surgery is considered.

Some doctors recommend surgery in special situations such as in men whose tumors are at an advanced stage, or in women who want to become pregnant (the drugs must be stopped during pregnancy, and pregnancy might cause the tumor to grow quickly). Surgery can also be used to treat very large tumors after first shrinking them with drug treatment.

Radiation may be used if drug treatment and surgery are not successful.

Treatment of growth hormone-secreting adenomas

Adults with these tumors often have acromegaly, while children have gigantism.

Surgery is usually the first treatment for these adenomas, although often it can’t remove all of the tumor. If growth hormone and insulin-like growth factor-1 (IGF-1) levels remain high after surgery, many experts recommend treating with medicine first. Radiation therapy is another option, although it is used most often when drug treatment doesn’t work. This is because radiation is very slow to act and over time it can lead to lowered levels of other pituitary hormones.

Octreotide (Sandostatin), lanreotide (Somatuline Depot), and pasireotide (Signifor LAR) are man-made forms of the natural hormone somatostatin that return IGF-1 to normal levels in about two thirds of patients. They are taken as injections, usually about once a month. The dose of these drugs may need to be adjusted based on blood IGF-1 levels.

Because these drugs work well and only need to be given monthly, doctors have started to question whether surgery should always be the first treatment for people with growth hormone-secreting adenomas. In those who might have problems with surgery, such as people with other major health problems, these drugs might be a good choice as the first treatment.

Sometimes, drug treatment may be given for a short time before surgery. This may cause the tumor to shrink, which could improve the chance that the surgery will remove all of the tumor, but doctors can’t be certain before trying that this will help.

Another drug, pegvisomant, works by blocking the action of growth hormone. It can be used if somatostatin analogs (octreotide, lanreotide, or pasireotide) aren’t doing enough to block growth hormone production.

Drugs such as cabergoline or bromocriptine can reduce growth hormone levels in about 1 out of 5 patients. Unfortunately, some patients have trouble tolerating the high doses often needed for these drugs to be effective. The main advantage of these drugs is that they are in pill form.

If surgery and drug treatments don’t work, then radiation therapy may be used.

Treatment of corticotropin (ACTH)-secreting adenomas

Surgery is usually the main treatment. If the surgery doesn’t remove the tumor completely or if it grows back, the 2 main options are a second surgery or radiation therapy. Radiation can often take months or years to work, so medicines may be given to help control cortisol levels in the meantime.

If surgery and radiation don’t control cortisol levels, treatment options may include using medicines or removing both of the adrenal glands (see below).

Several different types of medicines can be used to help control cortisol levels or limit the effects of this hormone in the body (see “Medicines to treat pituitary tumors”). Unfortunately, medicines aren’t always as effective in ACTH-secreting tumors as they are in some other types of pituitary tumors, and some of these drugs can have serious side effects that make them hard to take for long periods of time.

If medicines aren’t helpful, or if the patient can’t take them because of side effects, both adrenal glands can be removed with an operation called a bilateral adrenalectomy. This can usually be done with laparoscopic surgery, using several small incisions in the abdomen instead of one large one. The surgeon works through these small incisions with special long, thin instruments, including one with a tiny video camera lens on the end (called a laparoscope) for looking into the abdomen. Adrenalectomy stops all cortisol production, so high cortisol levels will no longer be a problem. But after the surgery patients will need to take pills to replace the adrenal steroid hormones for the rest of their life.

If the adrenal glands are to be removed, the pituitary gland will first be treated with radiation. If this isn’t done, removing the adrenals can cause the pituitary tumor to get larger and even start growing into the structures near the pituitary. This is known as Nelson syndrome. When the adenoma gets large, it can damage the normal parts of the pituitary gland, causing problems from hormone deficiency. It can also lead to high levels of ACTH. Because ACTH is similar to the hormone that causes tanning of the skin, the high ACTH levels make the skin darker.

Treatment of thyrotropin (TSH)-secreting adenomas

The treatment of choice for these tumors is usually surgery, sometimes along with radiation therapy. Radiation is not always helpful, and medicines may be needed to control the tumor’s hormone production. Some of the drugs that can be helpful include octreotide, lanreotide, cabergoline, and bromocriptine. These are used only if other treatments have failed to control the tumor.

It’s important to treat the pituitary tumor to prevent it from damaging nearby structures. Drugs that stop the thyroid gland from making thyroid hormone can actually make things worse because reducing thyroid hormone production may cause the TSH-secreting pituitary tumor to grow.

Treatment of gonadotropin (FSH/LH)-secreting adenomas

The hormones made by these tumors rarely cause major symptoms, so these tumors are often not found until they are large (macroadenomas) and pressing on nearby structures.

Follow up with frequent MRI scans will show if the tumor is growing back. If it is, options include radiation (if it hasn’t been given already) or medicines such as dopamine agonists (cabergoline, bromocriptine) or somatostatin analogs (octreotide, lanreotide).